Authorities have not said whether Prince had a prescription for the fentanyl and, if not, how he obtained it

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In this May 19, 2013, file photo, Prince performs at the Billboard Music Awards at the MGM Grand Garden Arena in Las Vegas.

One doctor delivered test results to Prince's home. Another sent his son, who wasn't a physician, on a cross-country flight to bring medication to the music star.

It's not clear if any doctor could have averted the fentanyl overdose that killed the singer in April. But his death may offer evidence for how the special treatment often afforded the rich and famous can result in worse health care than ordinary Americans receive. It's a pattern identified in medical literature as early as 1964 and it has a name: "VIP Syndrome."

Experts agree that doctors treating Michael Jackson and Joan Rivers lost their bearings and made fatal mistakes in the glare of their patients' fame. Eleanor Roosevelt is another example.

"There are a number of red flags that go up," said Dr. Robert Klitzman, who directs Columbia University's bioethics master's program. "Prince was one of the wealthiest musicians alive. Did he get appropriate care? VIP Syndrome may have been involved."

First described by Dr. Walter Weintraub of the University of Maryland School of Medicine in a 1964 paper, VIP Syndrome is shorthand for how the influence of wealth and the allure of fame can cause doctors to veer into risky territory when they cater to the demands of a star or his entourage.

Stars may reject medical advice or demand ineffective or harmful treatments. Star-struck doctors may order unnecessary tests or not enough tests. Hospital administrators may meddle in decisions if the patient is a potential financial donor.

Jackson's personal doctor, Conrad Murray, spent two years in prison after his involuntary manslaughter conviction in the King of Pop's 2009 death. Jackson had requested a surgical anesthetic, propofol, to help him sleep, calling it his "milk," according to trial testimony. Prosecutors said Murray supplied the drug and didn't notice when Jackson stopped breathing.

Eagerness to please apparently pushed Murray far beyond the boundaries of reasonable treatment, said Dr. Stephen Dinwiddie of Northwestern University Feinberg School of Medicine.

Another doctor took a cellphone photo of Joan Rivers on the operating table, according to a recently settled malpractice lawsuit. That's a clear sign of clouded judgment, Dinwiddie said.

The comedian's family accepted an undisclosed amount to settle the complaint in her 2014 death following a routine endoscopy. The family alleged doctors performed an unauthorized medical procedure and failed to act as Rivers' vital signs deteriorated.

Eleanor Roosevelt may have been misdiagnosed because of VIP Syndrome, said New York University School of Medicine's Dr. Barron Lerner, who published a paper based on his review of her medical record.

The first lady died in 1962 of tuberculosis, which could have been caught earlier if she'd had a bone marrow biopsy in time, Lerner said. Instead, she was misdiagnosed with aplastic anemia and treated with steroids, which may have reduced her body's ability to fight infection.

"Lots of doctors were involved, and no one was specifically in charge," Lerner said, citing one hallmark of VIP Syndrome. "She was an opinionated patient, and that made it more challenging to take care of her."

The timeline of events surrounding Prince suggests missed opportunities, experts said, including a close call less than a week before he died on April 21.

On April 15, Prince's private plane made an emergency stop in Illinois on a flight from Atlanta back to Minnesota. The Associated Press and other media organizations, citing anonymous sources, reported that first responders gave him an antidote commonly used to reverse suspected opioid overdoses.

"You'd think someone would say, 'Let's get him into treatment,'" Klitzman said. Instead, a week passed before Prince's associates called a California addiction and pain specialist, Dr. Howard Kornfeld.

Authorities have not said whether he had a prescription for the fentanyl and, if not, how he obtained it.

Much about the musician's care remains unknown. Was Prince — who reportedly suffered from hip and knee pain related to years of athletic stage performances — already seeing doctors well-versed in the risks of opioids? If he became addicted to painkillers, did anyone consider referring him to a nearby and highly regarded treatment option, Minnesota's Hazeldon Betty Ford?

Kornfeld sent his son Andrew in an effort to persuade Prince to seek long-term care at his Recovery Without Walls center in Mill City, California, according to William Mauzy, the Kornfelds' attorney. Andrew Kornfeld carried a small dose of buprenorphine, which is used to ease withdrawal symptoms and cravings, Mauzy has said.

The younger Kornfeld arrived too late. He was among those who discovered Prince's body.

Schulenberg saw Prince on April 7 and 20, the day before he died. He told investigators he prescribed medications for him, but a search warrant did not specify which drugs. Schulenberg arrived "on the death scene" at some point, according to the warrant. He told a detective he was there to drop off test results.

That house call suggests VIP Syndrome, Klitzman said.

Schulenberg's attorney, who would not comment specifically about Prince, said the doctor has made periodic house calls ever since he was in residency, when he was trained to do them.

During the visits, he carries only a stethoscope and "does not administer medications or perform any type of procedures in a patient's home," attorney Amy Conners said in an email to The Associated Press.

To guard against VIP Syndrome, the Cleveland Clinic published nine principles of caring for VIPs in 2011. The document warns doctors against bending the rules.

In the end, doctors must monitor a tendency toward any unusual practices, said Lerner, author of "When Illness Goes Public: Celebrity Patients and How We Look at Medicine."

"When you're contemplating superhuman or very heroic, unorthodox behavior in your zeal to help a famous patient," Lerner said, "that's where you've got to take a deep breath and reassess."